In the posthumously published Behind the eye , the late D.M. MacKay gave the definitive statement of his position on determinism and responsibility. This position relies heavily on two basic insights: first, a prediction of a human being's future states is not accurate if the subject of the prediction believes it; second, a proposition is true only if some agent's ability to exert control depends upon the accuracy of the proposition. In this essay, I develop an argument for the incompatibility of determinism and responsibility, as well as a counter argument which takes advantage of the preceding two insights. Next, I clarify MacKay's conception of truth and apply it to these arguments. Lastly, I defend MacKay's position against three possible criticisms.